On Wed, Nov 1, 2023 at 5:34 PM Yonghong Song <yonghong.song@xxxxxxxxx> wrote:
>
>
> On 11/1/23 3:42 PM, Andrii Nakryiko wrote:
> > On Wed, Nov 1, 2023 at 7:18 AM Lorenz Bauer <lorenz.bauer@xxxxxxxxxxxxx> wrote:
> >> On Tue, Oct 31, 2023 at 6:24 PM Andrii Nakryiko
> >> <andrii.nakryiko@xxxxxxxxx> wrote:
> >>>> Did you get round to fixing this, or did you decide to leave it as is?
> >>> Trying to recall, was there anything to do on the libbpf side, or was
> >>> it purely a compiler-side change?
> >> I'm not 100% sure TBH. I'd like clang to behave consistently for
> >> local_id and target_id. I don't know whether that would break libbpf.
> >>
> > *checks code* libbpf just passes through whatever ID compiler
> > generated, so there doesn't seem to be any change to libbpf. Seems
> > like compiler-only change. cc'ing Eduard as well, if he's curious
> > enough to check
>
> Okay, let us try to have a consistent behavior in local/remote type_id
> by changing local_id semantics to be the same as target_id.
>
> The corresponding llvm change is similar to
>
> [yhs@devbig309.ftw3 ~/work/llvm-project (ed)]$ git diff
> diff --git a/llvm/lib/Target/BPF/BPFPreserveDIType.cpp b/llvm/lib/Target/BPF/BPFPreserveDIType.cpp
> index 78e1bf90f1bd..1fbe1207dc6e 100644
> --- a/llvm/lib/Target/BPF/BPFPreserveDIType.cpp
> +++ b/llvm/lib/Target/BPF/BPFPreserveDIType.cpp
> @@ -86,15 +86,17 @@ static bool BPFPreserveDITypeImpl(Function &F) {
> Reloc = BTF::BTF_TYPE_ID_LOCAL;
> } else {
> Reloc = BTF::BTF_TYPE_ID_REMOTE;
> - DIType *Ty = cast<DIType>(MD);
> - while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
> - unsigned Tag = DTy->getTag();
> - if (Tag != dwarf::DW_TAG_const_type &&
> - Tag != dwarf::DW_TAG_volatile_type)
> - break;
> - Ty = DTy->getBaseType();
> - }
> + }
> + DIType *Ty = cast<DIType>(MD);
> + while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
> + unsigned Tag = DTy->getTag();
> + if (Tag != dwarf::DW_TAG_const_type &&
> + Tag != dwarf::DW_TAG_volatile_type)
> + break;
> + Ty = DTy->getBaseType();
> + }
>
> + if (Reloc == BTF::BTF_TYPE_ID_REMOTE) {
> if (Ty->getName().empty()) {
> if (isa<DISubroutineType>(Ty))
> report_fatal_error(
> @@ -102,8 +104,8 @@ static bool BPFPreserveDITypeImpl(Function &F) {
> else
> report_fatal_error("Empty type name for BTF_TYPE_ID_REMOTE reloc");
> }
> - MD = Ty;
> }
> + MD = Ty;
>
> BasicBlock *BB = Call->getParent();
> IntegerType *VarType = Type::getInt64Ty(BB->getContext());
>
> Either Eduard or Myself will submit a llvm patch to fix this in llvm18.
Sounds good, and thank you!
>
> >
> >
> >> Lorenz
